There is nothing wrong in reading the same Qur’anic verse(s) or Surah in each of the first two rak`ahs after reciting Al-Fatihah. Dr. Abdul-Fattah Idrees, professor of Comparative Jurisprudence at Al-Azhar University, states: Reciting a Qur’anic Surah after Al-Fatihah or any other verse(s) is a Sunnah in the first two rak`ahs (Prayer units). However, if one is unable to recite any verse(s) or Surah after reciting Al-Fatihah, then his Prayer remains valid.
On the other hand, if one is accustomed to reciting the same verse or Surah following the recitation of Al-Fatihah for the simple reason that he does not memorize any other verses or Surahs or he finds it easier to recite this specific verse or Surah, there is nothing wrong in that.